Treatment of hydrocarbons



All@ 8, 1944- H. R. l.JCJHNsoN 2,355,078 v TREATMENT 0F HYDROCARBONS Filed NOV. l,l 1943 .Pdced (Zrafye Patented Aug. 8, 1944 2,355,078 TREA'rtmNT or mno-cannons Harley R. Johnson, Tulsa, Application November 1, 1943, Serial No. 508,498

s calms. (c1. 252-322) l This isa continuation-in-part of Imy copending applications Serial Numbers 415,380 and 415,381 nled October 17, 1941.

This invention relates to a process for treating oils to remove foreign material therefrom. More particularly, it relates to the removal of salt and other undesirable suspended inorganic materials from crude petroleum oils. Still more specifically, it relates to desalting crude `oils `which contain crystalline salt suchas sodium quence, methods employing the Washing of the,

crude oil with hot water are'not effective in reducing the salt content to an acceptable figure. Thus, the reduction of salt content to less than pounds of salt per 1000barrels of oil is, in many instances, technically dicult and economically not feasible. `offers a method for accomplishing the economic reduction of salt content of crude oils to a relatively loW` gure.

The presence of salt, either in the Iorm of an emulsion or of` suspended crystals is objectionable because of the fact that when the oil is cracked, the salt accelerates the deposition of foreign material including coke in the-tubes and other parts of the plant, resulting in increased costs for clean-outs and shorter period of operation. By removing salt and other foreign Inaterial it is possible to improve the results obtained in the cracking plant.

In a -broad aspect the present invention relates' to steps in a process for the desalting of oil which The present invention ture not in excess of about 200 F., passing the mixture through a pool of brinegseparating the oil from the brine, passing the oil substantially free of brine through a bed of porous filtering material which lwill not disintegrate under the vconditions of treatment, simultaneously introducing Water to an intermediate point insaid bed of ltering material in order to maintain the same in a wet condition, and thereafter treating^ theoil to separate the salt therefrom.

The exact manner in which the brine treatment followed by the filteringl treatment func.

tions is. not fully understood. It is known that,

asmall amount of solid suspended material such as shale or mud, including some salt, is removed 'but the 4salt content of the oil is rarely reduced more than about 20-25,% and the reduction is not of a commercially feasible amount Microscopic examination of an oil containing suspended salt crystals sho'ws .that they lvary in size in the oil a's it is produced. The crystals appear to become of a more uniform size after passage through the brine treatment and the vfiltering step. Another important function of these steps appears to be the breaking up or disintegration of the lm of oil or asphaltic material surrounding the suspended salt crystals in such a manner that conventional desalting methods may subsequently be employed in order to dissolve the salt particles. invention may be considered as a step in .preconditioning the crude oil to convert the salt particles into a form that they may be readily removed by known methods, including treatment with water at an elevated temperature, electrical precipitation, etc.

One embodiment ',of the invention `is illustrated in the accompanying drawing which is diagrammatic and should not be construed as unduly limiting the invention.v

The salt-containing crude oil is introduced to the process through line i, valve 2, pump 3, line ent. The oil is' mixed with water introduced to the process through line t, valve l, pump B, liney 9 and valve i0 into line 5. 'I'he water introduced through line t may or may not be preheated, as

Thus, in a broad aspect, the present desired, and preferablyis treated water as, for example, boiler Water which has been heated to reduce its total hardness.l The mixture of oil and water are passed through heat exchanger I I Aor its-equivalent whereinv the mixtureis heated to an elevated temperature which generally will not be in excess of about 200 F. Actual operations have shown that temperatures in excess of 200 F. will effect greater salt'removal in the filtering step of the process than is obtained at temperatures below 200 F., but the salt content of the crude oil after the final stage of the process is higher, and-it is for this reason" that the mixture is heated to temperatures of below about 200 F. in heat exchanger II.

. In some cases, it may be desirabletto commingle a neutralizing agent with the oil and/or water. The neutralizing agent may be alkaline or acidic, depending upon whether the oil undergoing treatment is acid or alkaline.

The heated mixture of oil, water and neutralizing agent, if employed, is passed through line I2 containing valve I3 into packed tower I4, preferably through some sort of spray arrangement indicated at I5. A pool of brine is maintained in the lower portion of this tower below the packing. This phase of the treatment may also be carried out in a separate vessel. Any suitable method. of controlling the ,liquid level in the lower portion of tower I4 may be employedsuch as liquid level controller I6 which actuatesvalve I1 in line I8. When desired, a regulated portion of the brine withdrawn from line I8 may be supplied, by well known, means Anot illustrated, into line 4 to commingle with the oil and thus may replace all or a portion of the water introduced thereto through lines 6 and9.

' tact with the oil and/or water under the condi-` In practical operations it has been found that improved results are obtained when the level of brine in tower I4 is maintained below the packing as otherwise there is a tendency of the brine) and oil^to ood the tower and overflow.

The brine solution used may vary considerably incomposition but the optimum range of 'concentration has been found to be `about 3-10% by weight of salts, ofwhich sodium chloride may form a major constituent. `The quantity of brine is usually about 2-15% by volume, basedv upon the crude oil.- charge. It has been -found that the use of brine gives superior results over those obtained with pure water.

The lentering mixture of oil and .water passes upward throughthe pool of brine and a separation of oil from brine occurs. The oil substantially free of brine is then passed upwardly through the tower which contains a porous ltering material. By `thevterminology substan-.

tially free of brine, itis not intended to exclude'theV oil containing a minor amount of water and the amount of water will usually be below 4% by volume of the oil.

' 'by diverting a portion of the water introduced through linev and passing the same through line I9 containing'valve 20 into an intermediate point in the bed of filtering material. The exact point of introduction will depend upon the velocity of introduced at an intermediate point in tower Il may replace at least a part of the water commingled with the oil in line' I'.

The design of tower I4 is not limited to any one particular form and may comprise any suitable type of apparatus in order to obtain the desired contacting. One satisfactory apparatus consistsof a vertical shell containing bubble decks from which the caps have been removed and the filtering material disposed on the trays, so that the upwardly rising oil is passed, through the ltering material by way oa tortuous path.

Any suitable packing material.. may be employed, but not necessarily with'equivalent results, and thus may comprise fibrous substances suchas excelsior, coarse saw dust, wood shavings,

hay, cereal straws, mineral wool, rock wool, as-

bestos, etc., or it may consistof granular porous,

materials suchas limestone, caliche of the limestone type, pumice, nre-brick and other porousA` materials which willv not disintegrate by contions of treatment. Excelsior is particularly beneiicial because of its form which permits a ready passage 'of the oil and at the same time affords satisfactory contact. After being. usedy fora considerable time, the filtering material loses its effectiveness and this may be restored in part' ter instead of oil. 1 v

The combined brine and filtering treatment effects comparatively little removal of salt from the oil as is shown by the fact that an oil enterp ing with about 20o pounds of salt'per -1000 .bar-

rels ofA oil leaves the top of the packed tower with only about 20% reductionin salt content.. AWhat the brine and filtering treatments accomplish is a preconditioning'pf the oil so that it is readily removable byA conventional methods which,` in the absence of the brine and filtering treatments, either cannot be done, or is accomplished only with difiiculty. j i

-The temperature maintained in the packed tower is substantially the same or slightly lower than that to which the mixture of oil and brine is heated, in exchanger II and thus will be in the range of from about 100 to about 200 F.

Relatively low pressures may be used but it must v l be sufficient to prevent'undue varporization.

oil in tower Il since itis desired that substanltially all of the water'A introduced by this means ilows downwardly in the tower in order to wet the ltering material. A smallamount of the-(A The upper portion of tower I4 is usually empty of packing material. It may serve as a 4means for separating any gas which is dissolved in the crude oil and which is liberated at thetemperature and pressure used. The gas passes out of the tower through line 2l and valve 22 which may be vactuated by liquid level controller. 23 or "its equivalent. This gas may be sent to a suit- -able recovery system or it may be sent to the crude oil fractionator.

The crude oil is withdrawn through line 2,4 rand valve 25 and now is in condition for the ready vremoval of the salt by conventional meth- The packing.'4 material Yshould be preferentially wetted by wa.-

ods. One suitable conventional method is illustrated in the drawing and this comprises passing the oil through line. 26 containing valve 21, and commingling therewith water entering through line 28 containing valve 29. Although not illustrated inthe drawing, it is within the' scope of the invention to .install a suitable mixing device in order to elect the desired mixing of the oil andl water. The mixture1 is then directed to pump 30 by means of which it is supplied through line 3| containing valve 32heat exchanger 33, line 36 and valve 35 into settler 36. The amount of water commingled with the oil in line 2B must be sumcient so that the deposition of salt does not occur to any appreciable extent in heat exchanger.33. It has been found that the amount of water in the oil at this stage must be at least 4% by volume and it is generally preferred to use a larger amount of water.

In heat exchanger 33 the mixture of oil and water is heated to a temperature above that employed in the brine and ltering treatments and this temperature may be Within the range of from about 200 to about 400 F. or more and usually of from about 280 to about 350 F. The pressure employed must be sumcient `in order to maintain the oil and water in liquid phase.

The water introduced through line 28 likewise is preferably comparatively soft and may comprise treated boiler water. Settler 36 ,may comprise any suitable settling zone and a horizontal settler as illustrated has been found satisfactory although the invention is not limited thereto. Water containing dissolved salts. is removed through line 31 and valve 38, and the desalted crude oil is removed through line 39 and valve ftlto subsequent consumption in the refinery.

It is understood that the system illustrated by settler 3B, although being the preferred method, is not the only method which may be used for effecting the separation of the salt from the oil. Any other suitable method may be employed including, for example,electrical precipitation methods.

The following examples illustrate 4the process of the invention but not with the intention of unduly limiting the same.

Example -I from the excelsior tower is lower. 'I'his iskshown in the following table:

. Final' salt Salt removal in packed tower, percent Example III Final salt content #/l,000 barrels Inlet-temperature oi packed tower, "F.`

Example IV In an operation such as described in Example I but utilizing granular caliche as the packing'material, it was found that the crude oil is reduced to a salt content of less'than 20 pounds per 1000 barrels of oil when subsequently treated in a system similar to that described in connection with using 5% by volume of a 6% brine solution at Example II when operating substantially in the manner' described in Example I and varying the percent of salt` removed in the excelsior tower by modifying conditions accordinglv, it has been found that lower salt contents of the final crude oil are obtained when the percent of salt removed settler 30.

I claim as my invention:

l. In a process for the desalting ofXoil, the steps which comprise treating the oil with a brine solution at an elevated temperature not in excess ci about 200 F., separating the oil from. the brine solution, and contacting the oil substantially free of brine with a porous filtering material which will not disintegrate under the conditions of treatment and which is maintained in a wet condition. l

2. The process of claim 1 further characterized in that said filtering material comprises excelsior.

3. The process of claim l'further characterid in that said filtering material comprises caliche of the lime-stone type.

4. A process for desalting crude oil which comprises'vtreatinf the oil with a brine solution at an elevated temperature not in excess of about 200 F., separating the oil from the brine solution, contacting the oil substantially free of brine with a porous filtering material which is preferentially wetted by water and which will not disintegrate under the conditionsof treatment, and thereafter treating, the oil vto separate the salt therefrom.

brine through a bed of porous lterlng material I which will not disintegrate underthe conditions of treatment, and which is maintained in a wet arate the salt therefrom.

6. A process for desalting crudeoilwhich comprises mixingr the oil with water, heating the mixture to y,anelevs'ited temperature not in excess 5 of about 200 F., passing the mixture through y pool of brine solution, separating the oil from the brine,` passing the oil s\ibsi'.mtia11yv free 'of brine condition, and thereafter treating the oil to sep- `through a bed of porous filtering material which will not disintegrate under the conditions of treatment, simultaneously introducing water to an invAwermeoime point in said bed of nitermg material in order to maintain the same in a wet condition,

and thereafter treating. the oil to separate the salt therefrom.

HARLEY R. JOHNSON. 

